In wired communication systems, like for example wired Ethernet, data is provided to an end node via the data path given by a cable connecting the end node's network interface and a data forwarding device on the communication network. In state of the art wireless communication systems, RF signals are used for data communication between an end node and data forwarding device on the communication network. Although RF signals can be transmitted through walls, a sufficient number of wireless RF access points is required to guarantee that a user will obtain a proper connection to the communication network. However, a dense distribution of RF transceivers will occupy bandwidth in the spectrum, effectively limiting bandwidth available to each connected end node.
A new type of communication networks is emerging, where the communication is performed by light waves. Light sources may be used to transmit data to a receiver. The light waves may be visible or invisible to the human eye. A major difference to RF signalling is that light signals are line-of-sight-connections that will be obstructed by obstacles such as walls. A light source may be a luminaire normally used for illumination lighting of a space in a building, e.g. a luminaire that produces artificial light to illuminate the surrounding area. A system using such light sources for data communication is also known as a Visible Light Communication (i.e. VLC) system. Since a VLC system's main objective is high quality illumination lighting, the data transmit rates are limited by requirements imposed by their primary function. Light sources primarily used for illumination lighting are therefore generally slower data transmission devices. In order to achieve higher transmission data rates data transmission light sources that are not primarily tailored at illumination lighting may be used alternatively or in addition. Examples are for instance—but not limited to—emitters using changes in light levels (on, off, dimming, colours), using multiple colours simultaneously (e.g. RGBW), a laser source or IR or UV sources. These latter examples work best with a specific receiver, such as for example an optimized photo detector.
From US 2009157309 A1 a navigation system using messages in a visible light communication system is known. After having received a broadcast message via all lights installed in a building offering the navigation service, the user may subscribe to the service. The user may submit a desired destination to a central navigation map server. In return, the navigation map server provides a map including direction information via the light(s) identified in the vicinity of the user.
The article “Heterogeneous WI-FI and VLC (RF-optical) wireless architecture” by F. Duvnjak et al., 23rd International Conference on Software. Telecommunications and Computer Networks (SOFTCOM), University of Split, pages 310-314, 16 Sep. 2015 discloses a visible light communication system in which resource allocation is optimised by position information of the user devise obtained from optical light sources. In application control systems, such as for instance a lighting control system in a building, actuators (i.e. the lights) are typically installed at rather short distances, e.g. every few meters. When those actuators are used to emit data signals using light, a very dense network of emitters is established within a particular area. In state of the art optical communication systems, it is a challenge to properly deliver data to the receiving end node, especially when the end node is mobile and in transit (i.e. a person carrying a mobile receiver device). The main problem with such systems is that when the system does not know where the mobile receiver device is located at present, it may inject its data using all emitters, in the hope that the receiver device will pick it up. Such an approach limits the effective bandwidth within the network and does not scale well with a larger number of mobile end-nodes serviced within the same optical communication system.